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United States Patent |
6,196,348
|
Yano
,   et al.
|
March 6, 2001
|
Driving system for a working vehicle
Abstract
A first hydraulic pump P1 driven by power of an engine and a first
hydraulic motor M1 are fluidly connected so as to form a closed fluid
circuit. An output shaft 2 of first hydraulic motor M1 is drivingly
connected with a subtransmission 3. The output power from sub-transmission
3 drives main-driving wheels 5 and also drives a second hydraulic pump P2
fluidly connected with a second hydraulic motor M2 for driving sub-driving
wheels 6. A clutch 7 is interposed between an output shaft 4 of
sub-transmission 3 and an input shaft 9 of second hydraulic pump P2 or on
the output side of second hydraulic motor M2. Second hydraulic pump P2 or
second hydraulic motor M2 has variable displacement, so that second
hydraulic motor M2 is drivingly accelerated in proportion to the degree of
turning operation of a steering operating tool 31. In case that a
plurality of front reel mowers 8FL, 8FM and 8FR are disposed in front of
the vehicle body, a pair of decelerator casings 29 are disposed on both
lateral sides of transmission casing 1 for driving main-driving wheels 5.
Decelerator casings 29 project horizontally forward and support
main-driving wheels 5 respectively at their front portions. Middle front
reel mower 8FM is disposed between left and right decelerator casings 29.
Inventors:
|
Yano; Kazuhiko (Amagasaki, JP);
Azuma; Toshiro (Amagasaki, JP);
Ohashi; Ryota (Amagasaki, JP)
|
Assignee:
|
Kanzaki Kokyukoki Mfg. Co., Ltd. (Hyogo-Ken, JP)
|
Appl. No.:
|
119631 |
Filed:
|
July 21, 1998 |
Foreign Application Priority Data
| Jul 22, 1997[JP] | 9-195998 |
| Jul 25, 1997[JP] | 9-200403 |
Current U.S. Class: |
180/242; 180/305 |
Intern'l Class: |
B60K 017/356 |
Field of Search: |
180/242,243,247,248,305,307
|
References Cited
U.S. Patent Documents
3702642 | Nov., 1972 | Greene | 180/243.
|
3874470 | Apr., 1975 | Greene | 180/243.
|
3913697 | Oct., 1975 | Greene | 180/242.
|
3994353 | Nov., 1976 | Greene | 180/242.
|
4399886 | Aug., 1983 | Pollman | 180/242.
|
4771852 | Sep., 1988 | Nishikawa et al. | 180/247.
|
4886142 | Dec., 1989 | Yamaoka et al. | 180/242.
|
4991678 | Feb., 1991 | Furuya et al. | 180/248.
|
5074580 | Dec., 1991 | Wagner et al. | 180/242.
|
5080187 | Jan., 1992 | Asano et al. | 180/248.
|
5687808 | Nov., 1997 | Watanabe et al. | 180/307.
|
6059064 | May., 2000 | Nagano et al. | 180/243.
|
Foreign Patent Documents |
2136371 | Sep., 1984 | GB | 180/242.
|
60-32127 | Mar., 1985 | JP.
| |
60-139533 | Jul., 1985 | JP | 180/242.
|
9-121645 | May., 1997 | JP.
| |
Primary Examiner: Hurley; Kevin
Assistant Examiner: Cuff; Michael
Attorney, Agent or Firm: Sterne, Kessler, Goldstein & Fox P.L.L.C.
Claims
What is claimed is:
1. A driving system for a working vehicle comprising:
main-driving wheels;
sub-driving wheels;
a first hydraulic pump driven by power from an engine;
a first hydraulic motor fluidly connected with said first hydraulic pump,
so as to form a closed fluid circuit;
a transmission drivingly connected with an output shaft of said first
hydraulic motor;
a second hydraulic motor for driving said sub-driving wheels; and
a second hydraulic pump fluidly connected with said second hydraulic motor,
wherein output power from said transmission drives said main-driving
wheels and also drives said second hydraulic pump.
2. A driving system for a working vehicle as set forth in claim 1, further
comprising:
a clutch interposed between said main-driving wheels and said second
hydraulic pump or between said second hydraulic motor and said sub-driving
wheels.
3. A driving system for a working vehicle as set forth in claim 2, wherein
said clutch is an over-running clutch or a manual clutch.
4. A driving system for a working vehicle as set forth in claim 1, wherein
said second hydraulic pump or said second hydraulic motor has variable
displacement.
5. A driving system for a working vehicle as set forth in claim 1, further
comprising:
bevel gears; and
a differential gear unit for said main-driving wheels, wherein said output
shaft of said first hydraulic motor and an output shaft of said
transmission are disposed longitudinally, so as to transmit power to said
differential gear unit through said bevel gears.
6. A driving system for a working vehicle comprising:
main-driving wheels;
sub-driving wheels;
a first hydraulic pump driven by power from an engine;
a first hydraulic motor fluidly connected with said first hydraulic pump,
so as to form a closed fluid circuit;
a transmission drivingly connected with an output shaft of said first
hydraulic motor;
a first differential gear unit for driving said main-driving wheels;
a second hydraulic pump, wherein output power from said transmission drives
said first differential gear unit and also drives said second hydraulic
pump;
a second hydraulic motor fluidly connected with said second hydraulic pump;
and
a second differential gear unit for driving said sub-driving wheels,
drivingly connected with said second hydraulic motor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving system for a four-wheel drive
working vehicle comprising a hydrostatic transmission (an HST) for driving
main-driving wheels, a hydraulic pump, and one or more hydraulic motors
for driving sub-driving wheels, wherein output power from the hydraulic
motor of the HST for the main-driving wheels is partly transmitted to the
hydraulic pump for the sub-driving wheels through another transmission.
The present invention also relates to a construction for decelerating the
main-driving wheels, wherein a working machine is provided in front of a
vehicle body.
2. Related Art
Japanese Utility Model Laid-Open No. Sho 60-32127, for example, discloses a
conventional four-wheel drive vehicle provided with an HST. An engine
drives a hydraulic motor through a hydraulic pump fluidly connected with
the hydraulic motor. The hydraulic motor transmits power to a differential
gear unit through a mechanical sub-transmission for the purpose of driving
main-driving wheels (rear wheels or front wheels). The hydraulic motor
also partly transmits power to another differential gear unit through a
transmitting shaft for the purpose of driving sub-driving wheels (front
wheels or rear wheels).
Also, Japanese Laid-Open No. Hei 9-121645, for example, discloses a
conventional working vehicle having a working machine such as a mower
provided either in front of the vehicle body or at its venter portion
between its front wheels and rear wheels.
In this conventional construction, the rotary speed of the sub-driving
wheels is different from that ofthe main-driving wheels because the
main-driving wheels receive the transmitted power through the
sub-transmission. Thus, a problem exists whereby the faster wheels, which
are either the main-driving wheels or the sub-driving wheels (the front
wheels or the rear wheels), drag the other wheels and a working machine
provided on the vehicle. This can cause significant injury to the ground
surface (e.g., of a farm), especially if the working vehicle is provided
with a mower.
Even if the rotary speeds of the main-driving wheels and the sub-driving
wheels (front and rear wheels) are equalized, the four-wheel drive working
vehicle turns around an inside main-driving wheel. Therefore, the rotary
speed of both sub-driving wheels, which are rather apart from the inside
main-driving wheel, slows down so as to be dragged. When the working
vehicle travels in two-wheel drive, where only the main-driving wheels are
driven, if one of either the left or the right main-driving wheels runs
idle, the other main-driving wheel slips because it cannot receive the
driving power. This also can cause injury to the ground surface.
For the latter construction, a plurality of mowers are occasionally
juxtaposed on a lateral row (arranged on in the center, one on the left
and one on the right, for example), so that they can cut the grass in a
wide lateral range. In this case, the mowers overlap one another when
viewed from the front, so as to leave no uncut grass.
Consequently, these mowers do not overlap when viewed from the side. This
causes the size of the working vehicle to increase longitudinally.
Furthermore, a center mower of the arrangement must be vertically and
movably suspended by a long arm. Accordingly, it is necessary to reinforce
the strength of the arm and the lifting power thereof, especially when the
center mower is disposed at the fore-end of the vehicle body (before left
and right mowers). Additionally, for preventing the vehicle with the
mowers from turning along a large turning radius, the overlapping portions
of the center mower with the left and right mowers are necessarily
lengthened, thereby causing much unevenness of the cut between the portion
where the mowers overlap and the portion where they do not overlap.
Where the mower is disposed at the venter portion of the working vehicle
between the front wheels and the rear wheels, a transmitting shaft is
necessarily interposed between the output shaft of the hydraulic motor and
the differential gear unit of the sub-driving wheels (front wheels or rear
wheels), thereby restricting the space for disposal of the mower.
SUMMARY OF THE INVENTION
The first object of the present invention is to provide a driving system
which can prevent a working vehicle that is provided with a working
machine such as a mower from injuring the ground surface (e.g., of a
farm), especially while the working vehicle is turning.
To achieve the first object, in the case of a four-wheel drive working
vehicle, a first hydraulic pump driven by the power of an engine and a
first hydraulic motor for driving the main-driving wheels are fluidly
connected with each other through a closed fluid circuit. This arrangement
allows the rotary speed of the sub-driving wheels to correspond to the
rotary speed of the main-driving wheels and prevents the working vehicle
from dragging the working machine, especially during turning. An output
shaft of the first hydraulic motor is drivingly connected with a
transmission, so that power transmitted through the transmitting mechanism
is given to a first differential gear unit for driving the main-driving
wheels and a second hydraulic pump for driving both sub-driving wheels.
The second hydraulic pump is fluidly connected to a second hydraulic
motor, which is drivingly connected with a second differential gear unit
for the sub-driving wheels. The second hydraulic pump or the second
hydraulic motor has variable displacement. A displacement adjusting means
like a swash plate of the hydraulic pump or the second hydraulic motor is
connected with a steering operating tool, so that the rotary speed of the
sub-driving wheels can correspond to the degree of turning operation of
the steering operating tool.
Alternatively, the second hydraulic pump may be fluidly connected with a
pair of second hydraulic motors, which respectively drive left and right
axles of the sub-driving wheels without the second differential gear unit.
The second hydraulic pump or the pair of second hydraulic motors have
variable displacement. A displacement adjusting means like a swash plate
of the hydraulic pump or those of the pair of second hydraulic motors are
connected with a steering operating tool, so that the rotary speed of the
sub-driving wheels can correspond to the degree of turning operation of
the steering operating tool.
In the construction wherein the pair of second hydraulic motors are
provided, the second hydraulic pump and the pair of second hydraulic
motors may also have fixed displacement. In this case, the steering
operating tool is connected with a flow control valve unit by oil passages
interposed between the second hydraulic pump and the pair of second
hydraulic motors, such that the oil displacements ofthe pair of second
hydraulic motors can be controlled by turning operation of the steering
operating tool.
The second object of the present invention is to enable a two-wheel drive
working vehicle employing the above mentioned driving system to quickly
recover from being stuck due to the slipping of both or either of the
main-driving wheels while the vehicle is turning.
To achieve the second object, when the working vehicle employing the above
mentioned driving system, which can be switched between four-wheel drive
and two-wheel drive, is set in two-wheel drive, the driving power of the
output shaft of the first hydraulic motor, which has been transmitted
through the transmission, is given to the main-driving wheels and is also
given to the sub-driving wheels through a clutch. The clutch acts as an
over running clutch or a manual clutch, and is interposed between an
output shaft of the first hydraulic motor and an input shaft of the second
hydraulic pump or on the output side of the second hydraulic motor (output
sides of the pair of second hydraulic motors).
The third object of the present invention is to enable a working vehicle
employing the driving system ofthe first object to be light and to be
longitudinally short or laterally narrow, thereby providing a small
turning radius. Additionally, the object is to allow a working vehicle
loaded in front of its vehicle body (its pair of front wheels) with a
working machine such as a mower to provide the support and the driving
power for vertical moving thereof.
To achieve the third object, the driving system for a working vehicle is
further constructed so that both of the output shafts of the first
hydraulic motor and the transmission, which are contained in a
transmission casing, are disposed in a longitudinal direction of the
vehicle so as to drive the first differential gear unit for the
main-driving wheels through bevel gears. This construction reduces the
lateral width of the transmission casing. Alternatively, both of the
output shafts of the first hydraulic motor and the transmission are
disposed in a lateral direction of the vehicle so as to drive the first
differential gear unit for the main-driving wheels, thereby reducing the
longitudinal length of the transmission casing.
Alternatively, in cases where the working machine is disposed in front of
the vehicle body, a pair of decelerator casings are disposed respectively
on both outer lateral sides of the left and the right front axle casings,
so as to project substantially forward in the horizontal direction. Wheel
shafts are supported respectively by front portions of the decelerator
casings and the pair of main-driving wheels are attached respectively to
the wheel shafts. The working machine is disposed between the left and the
right decelerator casings, thereby reducing the longitudinal length of the
vehicle body and providing the support and the driving power for its
vertical moving.
The fourth object of the present invention is to provide a working vehicle
with expanded space at the venter portion of the vehicle body between its
front and rear wheels for disposal of a working machine such as a mower.
To achieve the fourth object, the second hydraulic pump for driving the
sub-driving wheels, which receives the output power of the first hydraulic
motor through the transmission, is fluidly connected without a
transmitting shaft to the second hydraulic motor, which is drivingly
connected with the second differential gear unit for the sub-driving
wheels. Also, each of the decelerator casings contains a reduction gear
train interposed between the first differential gear unit, which is
contained in the front axle casing, and each of the main-driving wheels,
so as to reduce the ratio of deceleration of the first differential gear
unit, thereby compacting the front axle casing. Thus, the space at the
center portion of the vehicle body between the front and rear wheels can
be advantageously expanded for disposal of the working machine.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a side view of the whole of a working vehicle, which employs a
driving system of the present invention, provided with mowers as working
machines;
FIG. 2 is a schematic plan view of a working vehicle provided with mowers,
employing a basic driving system of a first group according to the present
invention;
FIG. 3 is an oil circuit diagram of the same driving system shown in FIG.
1;
FIG. 4 is a diagram ofthe same driving system, concerning the arrangement
of shafts in a transmission casing 1;
FIG. 5 is a diagram of the same driving system, also concerning the
arrangement of shafts in a transmission casing 1;
FIG. 6 is a diagram of an embodiment of the driving system including a
transmitting shaft between transmission casing 1 and sub-driving wheels 6;
FIG. 7 is a diagram of a driving system of the first group, wherein a
clutch 7 is disposed on the output side of a second hydraulic motor M2;
FIG. 8 is a diagram of a driving system of the first group, wherein the
second hydraulic motor M2 is drivingly changed by the turning operation of
a steering operating tool 31;
FIG. 9 is a diagram of another driving system ofthe first group, wherein
the second hydraulic M2 is drivingly changed by the turning operation of
steering operating tool 31;
FIG. 10 is a diagram of a basic driving system of the second group
according to the present invention;
FIG. 11 is a diagram of a driving system of the second group, wherein
clutches 7 are disposed on the output sides of a pair of second hydraulic
motors M3;
FIG. 12 is a diagram of a driving system of the second group, wherein the
pair of second hydraulic motors M3 are drivingly changed by the turning
operation of steering operating tool 31;
FIG. 13 is a diagram of another driving system of the second group, wherein
the pair of second hydraulic motors M3 is drivingly changed by the turning
operation of steering operating tool 31 through a flow control valve unit
44;
FIG. 14 is a diagram of an embodiment of a flow control valve unit 44;
FIG. 15 is a diagram of another embodiment of a flow control valve unit 44;
FIG. 16 is a diagram of another embodiment of a flow control valve unit 44;
FIG. 17 is a diagram of a driving system of the second group, wherein the
pair of second hydraulic motors M3 are drivingly changed by the detection
of a difference between the rotary speeds of the main-driving wheels 5 and
the sub-driving wheels 6;
FIG. 18 is a diagram of another driving system of the second group, wherein
the pair of second hydraulic motors M3 are drivingly changed by the
detection of a difference between the rotary speeds of the main-driving
wheels 5 and the sub-driving wheels 6;
FIG. 19 is a diagram of a driving system including a single sub-driving
wheel 6; and
FIG. 20 is a sectional plan view of a decelerator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Explanation will be given on an embodiment wherein the driving system of
the present invention is employed by a mower tractor. As shown in FIG. 1
and others, a pair of front wheels are the main-driving wheels 5 and a
pair of rear wheels are the sub-driving wheels 6, which are also used as
wheels for steering. Main-driving wheels 5 are supported at a front
portion of a vehicle body frame 19 and sub-driving wheels 6 are supported
at a rear portion thereof. Triple front reel mowers 8FL, 8FM and 8FR are
vertically and movably disposed in front of the mower tractor. Double left
and right side reel mowers 8SL and 8SR are vertically and movably disposed
between main-driving wheels 5 and sub-driving wheels 6. With regard to
triple front reel mowers 8FL, 8FM and 8FR, the left and right front reel
mowers 8FL and 8FR (a pair of side front reel mowers) project forward from
the front end of the vehicle body and the lateral middle front reel mower
(a middle front reel mower) 8FM is disposed behind the both of side front
reel mowers 8FL and 8FR. In some cases, only the middle front reel mower
8FM may be used. Above the front portion of vehicle body frame 19 is
disposed an operating portion A and behind the rear portion thereof is
disposed an engine E covered with a bonnet.
As shown in FIGS. 1 to 3, each of the left and right axle casings 52 is
fixed onto each of the left and right sides of a transmission casing 1 and
contains each of the left and right axles 18L, and 18R. Each of the left
and right decelerator casings 29 containing the reduction gear (bull gear)
train is disposed on the outer end of each axle casing 52 so that the
reduction gear train is interposed between each of axles 18L and 18R and
each of the main-driving wheels 5. According to this construction, the
ratio of deceleration by a first differential gear unit D1 can be so small
as to reduce the transmitting torque thereof, thereby enabling first
differential gear unit D1 to be minimized. Also, the width between treads
of main-driving wheels 5 can be changed by means of interposition of
decelerator casings 29.
Transmission casing 1, the left and right axle casings 52, and the left and
right decelerator casings 29 are arcuately arranged when viewed in plan,
so as to create a space P between the pair. Middle front reel mower 8FM is
disposed in space P so as to be between the left and right front wheels
(main-driving wheels 5). Thus, when triple front reel mowers 8FL, 8FM and
8FR are disposed at the front portion of the vehicle body, the whole of
the working vehicle provided with them can be longitudinally short. Also,
an arm for lifting middle front reel mower 8FM can be short, and lifting
mechanisms for vertically and movably suspending left and right front reel
mowers 8FL and 8FR can be disposed in space P so as to be protected. Thus,
space P between decelerator casings 29 can be advantageously utilized.
Also, the balance of weight of the mower tractor can be improved so as to
stabilize its durability in travel because ofthe disposal of middle front
reel mower 8FM at the center of the vehicle body.
Axle casings 52 may be integrally formed at the left and right sides of
transmission casing 1, or may be integral with decelerator casings 29.
As shown in FIGS. 2, 3 and 20, decelerator casings 29 project substantially
forward in the horizontal direction. They can also be disposed
substantially in the vertical direction so as to raise the level of axles;
however, the working vehicle of this embodiment provided for lawn mowing
prefers low axles so as to have a low center of gravity. Thus, decelerator
casings 29 are disposed substantially in the horizontal direction, thereby
enabling the vehicle provided with the mower or mowers to travel and work
easily and steadily on a slope or the like.
Basic portions of vertically moving links 50L and 50R, which vertically and
movably suspend front side reel mowers 8FL and 8FR respectively, are
pivoted onto the inner sides of decelerator casings 29 respectively.
Vertically moving links 50L and 50R are vertically rotated by a hydraulic
cylinder (not shown). Vertically moving links 50L and 50R can be shorter
as decelerator casings 29 project more forward. They also require no
bracket for attachment thereof. A vertically moving link 51 is pivoted at
its basic portion onto the front surface of transmission casing 1 and can
be vertically rotated by a hydraulic cylinder. Middle front reel mower 8FM
is suspended from an utmost end of vertically moving link 51, which is
rotatably supported at its basic portion by the front portion of
transmission casing 1, so as to be vertically rotated by operation of a
hydraulic cylinder.
As shown in FIG. 20, each decelerator casing 29, which can be laterally
separated into a left half casing 29a and a right half casing 29b, is
fixed onto an outer end of each axle casing 52. An utmost end portion of
axle 18 (which is axle 18L or 18R) is inserted into a rear portion of
decelerator casing 29 and is rotatably supported by a bearing. With regard
to the interior of decelerator casing 29, a small diametric gear 53 is
fixed onto the utmost end portion of axle 18. At a front space between the
inner sides of left and right half casings 29a and 29b of decelerator
casing 29 is rotatably supported a wheel shaft 55 through bearings. A
large diametric gear 54 is fixed onto an inner end portion of wheel shaft
55 and always engages with small diametric gear 53, thereby constructing a
reduction gear train. An outer end portion of wheel shaft 55 projects
laterally outward from decelerator casing 29, such that main-driving wheel
5 is fixed onto the outer projecting portion of wheel shaft 55.
The ratio of deceleration by first differential gear unit D1 can be reduced
because of the reduction gear trains contained in decelerator casings 29,
thereby reducing the torque for transmitting by first differential gear
unit D1. Thus, first differential gear unit D1 can be compacted, so as to
raise the bottom level of the vehicle, thereby expanding space P in its
longitudinal direction and the space between front and rear wheels. Also,
the width between both treads of main-driving wheels 5 can be extended
because of the interposition of decelerator casings 29 or axle casings 52
and can be adjusted if various kinds of decelerator casings 29 are
prepared.
Next, explanation will be given on various embodiments of driving systems
for driving of main-driving wheels 5 and sub-driving, wheels 6 as follows.
In this regard, the driving systems of the following embodiments are
roughly classified into first and second groups. For the purpose of
driving sub-driving wheels 6, each driving system of the first group uses
a single second hydraulic motor M2 and a second differential gear unit D2,
and each driving system of the second group uses a pair of second
hydraulic motors M3.
First, a construction of a first HST, which is common in the driving
systems of both the first and second groups will be described in
accordance with FIGS. 3 to 5. As shown in FIG. 3, a first hydraulic pump
P1 with variable displacement is connected to an output shaft of engine E.
A first hydraulic motor M1 with fixed displacement is attached to
transmission casing 1. First hydraulic pump P1 and first hydraulic motor
M1 are fluidly connected with each other through oil passages like
pipings, so as to constitute the first HST. An output shaft of first
hydraulic pump P1 is connected with an input shaft 2 supported by
transmission casing 1.
With regard to the interior of transmission casing 1, a sub-transmission 3,
which can be shifted stepwise, is contained therein. As shown in FIG. 3,
for example, sub-transmission 3 is so constructed that a large diametric
gear 10 and a small diametric gear 11 are fixed onto input shaft 2 and
double ridable gears 12 are provided on output shaft 4 so as to engage
with it through a spine, thereby being axially slidable and not relatively
rotatable. When a gear 12a of double slidable gears 12 engages with large
diametric gear 10, output shaft 4 is rotated quickly. When the other gear
12b thereof engages with small diametric gear 11, output shaft 4 is
rotated slowly. Thus, sub-transmission 3 can be shifted between two steps
of high and low speed states; however, it is not restricted to having two
speed steps. On the contrary, it may also have only one gear pattern or
more than two gear patterns, or may be also steplessly shifted.
A gear 13 is fixed onto one end of output shaft 4 and engages with a gear
15 provided on a deceleration shaft 14. Bevel gear 16 is also fixed onto
deceleration shaft 14 and engages with a ring gear 17 of first
differential gear unit D1. Axles 18L and 18R project from first
differential gear unit D1 and main-driving wheels 5 are drivingly
connected respectively to the utmost ends of axles 18L and 18R.
Accordingly, the driving power transmitted from first hydraulic motor M1
to output shaft 4 through sub-transmission 3 further drives first
differential gear unit D1 through gears 13 and 15 and bevel gear 16,
thereby driving main-driving wheels 5.
Other embodiments concerning an inner construction of transmission casing 1
will be described in accordance with FIGS. 4 and 5. In the above mentioned
embodiment shown in FIG. 2, transmission casing 1 contains input shaft 2,
output shaft 4, and input shaft 9, which are arranged perpendicularly to
axles 18L and 18R. In other words, they are arranged in a longitudinal
direction of the vehicle. In the embodiments shown in FIGS. 4 and 5, input
shaft 2, output shaft 4 and input shaft 9 are arranged in parallel to
axles 18L and 18R. In other words, they are arranged in a lateral
direction of the vehicle. Also, plain gear 16' and plain ring gear 17' are
provided respectively instead of bevel gear 16 and bevel ring gear 17 of
first differential gear unit D1. The other components are similarly
structured, as shown in FIG. 2.
With regard to the disposal of hydraulic pump P1 and motor M1, as shown in
FIG. 4, each is disposed apart from the other respectively on both lateral
outer sides of transmission casing 1. On the other hand, with regard to
the disposal of hydraulic pump P1 and motor M1, as shown in FIG. 5, both
are juxtaposed on one side of transmission casing 1.
Each of the above mentioned embodiments concerning the interior of
transmission casing 1 is shown in FIGS. 3 to 5, employed by the driving
system of the first group. However, the embodiments can be also employed
by the driving systems of the second group.
As shown in FIG. 3, with regard to oil circuits of the first and second
HSTs, first hydraulic pump P1 and a charge pump CP1 are driven
simultaneously. Oil passages 26a and 26b are interposed between first
hydraulic pump P1 and first hydraulic motor M1. A charge relief valve 27
is connected to a discharging oil passage of charge pump CP1 and to oil
passages 26a and 26b through a pair of check valves 28, so as to supply
the operating oil to the closed oil circuit of the first HST. Charge pump
CP1 of the first HST can also drive a working machine by pressure oil
discharged therefrom.
In such a construction, the rotary speed of output shaft 4 of first
hydraulic pump P1 is steplessly changed by changing the slanting angle of
a movable swash plate (as a displacement adjusting means) of first
hydraulic pump P1. This allows main-driving wheels 5 to be rotated at the
speed corresponding to the rotary speed of output shaft 4, thereby driving
the vehicle.
Next, an explanation will be given on a second HST embodied in the driving
systems of the first group. Output shaft 4 of sub-transmission 3 is
drivingly corrected with first differential gear unit D1 through gears, as
mentioned above, so as to drive main-driving wheels 5. Output shaft 4 is
also connected with an input shaft 9 of a second hydraulic pump P2.
Second hydraulic pump P2 is fluidly connected with second hydraulic motor
M2 through a pair of pipings 20 forming a closed fluid circuit, thereby
constituting the second HST. Second hydraulic pump P2 and motor M2 both
may have fixed or variable displacements or they may be constructed so
that one of them has variable displacement and the other has fixed
displacement, depending on their relation to the other components.
The oil circuit of the second HST, which includes a charge pump CP2 among
other elements, is constructed similarly to that of the first HST, as
shown in FIG. 3.
A bevel gear 22 is fixed onto an output shaft 21 of second hydraulic motor
M2 and engages with a ring gear 24 of a second differential gear unit D2
within a rear axle housing 23. Sub-driving wheels 6 are fixed respectively
onto the outer ends of left and right axles 25L and 25R, projecting
laterally from second differential gear unit D2.
As shown in FIG. 6, a transmitting mechanism including a universal joint 38
and a transmitting shaft 39 may be interposed between a shaft on the
output side of sub-transmission 3 (which is output shaft 9 on output side
of clutch 7 in the embodiment shown in FIG. 6) and second differential
gear unit D2 instead of the second HST. This construction simplifies the
power transmitting system therebetween.
Next, construction of a clutch 7 will be described with respect to the
driving system for sub-driving wheels 6. In the embodiments shown in FIG.
3 and others, clutch 7, acting as either an over-running clutch or a
manual clutch, is interposed between output shaft 4 of sub-transmission 3
and input shaft 9 of second hydraulic pump P2 with fixed displacement.
Alternatively, clutch 7, acting as an over-running clutch or a manual
clutch, may also be disposed on the output side of second hydraulic motor
M2 with fixed displacement, as shown in FIG. 7. In this case, output shaft
4 and input shaft 9 are directly connected with each other, such that
second hydraulic motor M2 always drives when hydraulic pump P2 drives.
Output (motor) shaft 21 of second hydraulic motor M2 is separated into a
driving motor shaft 21a and a follower motor shaft 21b and they can be
connected with each other through clutch 7. Follower motor shaft 21b,
which is a shaft on the follower side of clutch 7, is connected with axles
25L and 25R through bevel gear 22, differential ring gear 24 and second
differential gear unit D2.
Next, the operation of clutch 7 will be described. In cases where clutch 7,
which is interposed between output shaft 4 and input shaft 9 as shown in
FIG. 3, is an over-ruining clutch, clutch 7 engages between output shaft 4
and input shaft 9 when the rotary speed of input shaft 9 is slower than
that of output shaft 4. This engagement occurs without regard to the
rotary direction of the shafts (whether shafts 4 and 9 are rotated
regularly or reversely). The shafts disengage when the rotary speed of
input shaft 9 is the same as or faster than that of output shaft 4.
With regard to the driving of sub-driving wheels 6, sub-driving wheels 6
are rotated by friction against the ground surface when the vehicle
travels. This rotation drives second hydraulic motor M2 and discharges
pressure oil to second hydraulic pump P2, thereby driving its input shaft
9. Clutch 7, acting as an over-running clutch, automatically acts.
In this regard, clutch 7 engages when input shaft 9 rotates slower than
output shaft 4 and disengages when input shaft 9 rotates at the same speed
or faster than output shaft 4.
When the vehicle travels on a dry flat road, main-driving wheels 5 and
sub-driving wheels 6 are rotated at the same speed without slipping. In
this case, second hydraulic pump P2 and its input shaft 9 are driven by
pressure oil discharged from second hydraulic motor M2, which is driven by
the following rotation of sub-driving wheels 6. Clutch 7 automatically
disengages between output shaft 4 and input shaft 9 because output shaft 4
is rotated faster than input shaft 9. Thus, second hydraulic pump P2 is
not driven and sub-driving wheels 6 are prevented from dragging because
they are not being driven. This prevents injury to the ground surface.
In travel, when one of main-driving wheels 5 falls in mud or a hollow and
slips, the traveling speed of the vehicle is reduced whereas the rotary
speed of output shaft 4 is kept. This causes the rotary speed of
sub-driving wheels 6 to become slower relative to that of main-driving
wheels 5. Accordingly, the driving speed of second hydraulic motor M2 is
reduced, thereby decelerating input shaft 9 of second hydraulic pump P2.
Thus, clutch 7 automatically engages between output shaft 4 and input
shaft 9, such that second hydraulic pump P2 is driven by the rotation of
output shaft 4. This causes the driving of second hydraulic motor M2. As a
result, sub-driving wheels 6 are driven by second hydraulic motor M2, such
that the vehicle travels in four-wheel drive, thereby allowing the vehicle
to escape from mud or the like.
In cases where clutch 7, acting as an over running clutch, is disposed on
the output side of second hydraulic motor M2 with fixed displacement as
shown in FIG. 7, clutch 7 disengages when the rotary speed of driving
motor shaft 21a is the same as or less than that of follower motor shaft
21b. Conversely, clutch 7 automatically engages when driving motor shaft
21a is rotated faster than follower motor shaft 21b. According to this
construction, all of the four wheels are rotated at the same speed in
normal travel, so that main-driving wheels 5 drive second hydraulic motor
M2 through output shaft 4 and second hydraulic pump P2.
When clutch 7 automatically disengages, so that follower motor shaft 21b is
not driven, the vehicle travels in two-wheel drive. When either or both of
the main-driving wheels 5 slip, the traveling speed of the vehicle is
reduced, such that the rotary speed of sub-driving wheels 6 becomes
relatively slower as compared with that of main-driving wheels 5. Thus,
clutch 7 automatically engages between driving motor shaft 21a and
follower motor shaft 21b, thereby driving second differential gear unit
D2. As a result, sub-driving wheels 6 are driven by second differential
gear unit D2, so that the vehicle travels in four-wheel drive.
With regard to both embodiments shown in FIG. 3 and 7, clutch 7 may also
act as a manual clutch, which can be switched on and off by manual
operation of a lever. Alternatively, clutch 7 may also act as an
electromagnetic clutch, which can be switched by operation of a switch.
Furthermore, clutch 7 may also be constructed so as to engage when the
difference between the rotary speeds of the left and right axles 18L and
18R is recognized to be larger than the predetermined value detected.
Next, embodiments of construction for avoiding dragging in turning will be
described in accordance with FIGS. 8 and 9. For the embodiment shown in
FIG. 8, clutch 7 is made as an electromagnetic clutch, which can be
manually switched by operation of a switch or the like, or both of second
hydraulic pump P2 and second hydraulic motor M2 of the second HST (in this
embodiment, second hydraulic motor M2) have variable displacement. The
electromagnetic clutch and a movable swash plate of second hydraulic pump
P2 or motor M2 with variable displacement are connected to a steering
operating tool (a steering wheel) 31.
According to such a construction, when the vehicle travels in two-wheel
drive (only main-driving wheels 5 are driven), the electromagnetic clutch
is unconnected, so that sub-driving wheels 6 are steered by operation of
steering operating tool 31, similar to the conventional construction. When
either or both of main-driving wheels 6 slip, the switch is turned on so
as to connect the electromagnetic clutch, such that the vehicle travels in
four-wheel drive and escapes. In this construction, an over-running clutch
may also be provided in addition to the electromagnetic clutch, thereby
requiring no manual operation to switch the clutch between two-wheel drive
and four-wheel drive.
When the electromagnetic clutch is connected so as to strengthen the grip
of the vehicle on the ground for the purpose of stead travel, unless the
vehicle is stuck, the movable swash plate as a displacement adjusting
means of second hydraulic motor M2 is shifted so as to coincide the rotary
speed of sub-driving wheels 6 to that of main-driving wheels 5. In the
turning operation of steering operating tool 31, the degree of slanting of
the movable swash plate is reduced in inverse proportion to the degree of
rotation of steering operating tool 31. This causes the sub-driving wheels
6 to be accelerated, thereby preventing them from being dragged.
For the embodiment shown in FIG. 9, both the second hydraulic pump P2 and
motor M2 have fixed displacement. In addition, a bypass valve V is
interposed between the pair of pipings 20, so as to be connected to
steering operating tool 31. When steering operating tool 31 is rotated at
an angle more than the predetermined angle for turning, bypass valve V is
switched so as to communicate between pipings 20. Thus, second hydraulic
motor M2 is changed to be neutral, causing the vehicle to turn in
two-wheel drive. This operation prevents dragging, which is generated by a
difference between the rotary speeds of main-driving wheels 5 and
sub-driving wheels 6. In addition, means for detection of the oil pressure
of pipings 20 may also be provided. Valve V is switched to communicate
between pipings 20 when the oil pressure thereof is changed by the pumping
operation of the rotation of second hydraulic motor M2 during turning.
Next, explanation will be given on a driving system for sub-driving wheels
6, namely a modified second HST, embodied in the driving system of the
second group in accordance with FIGS. 10 to 19.
The modified second HST is so constructed that a pair of the left and right
second hydraulic motors M3, which have variable or fixed displacement, are
fluidly connected with second hydraulic pump P2 in parallel to each other,
instead of second hydraulic motor M2 and differential gear unit D2. In
this regard, an advancing oil passage 45a and a reversing oil passage 45b
acting like pipings are extended from second hydraulic pump P2. Also, a
pair of branching oil passages 45d are branched from each of the pair of
oil passages 45a and 45b, so as to be connected respectively to left and
right second hydraulic motors M3. Output shafts 30L and 30R project
laterally from left and right second hydraulic motors M3. Output shafts
30L and 30R constitute axles as they are described above. Otherwise, they
are directly connected at their outer end with axles, such that
sub-driving wheels 6 are attached to the outer ends of the axles.
An over-running clutch or a manual clutch is used as clutch 7 similar to
the clutch of the first group. For the embodiment shown in FIG. 10 and
others, clutch 7 is interposed between output shaft 4 of subtransmission 3
and input shaft 9 of second hydraulic pump P2. For the embodiment shown in
FIG. 11, a pair of clutches 7 are disposed on the output sides of left and
right second hydraulic motors M3. In this regard, each of output shafts
30L and 30R are separated into a motor shaft 30a of second hydraulic motor
M3 and an axle 30b onto which sub-driving wheel 6 is fixed. Each of the
pair of clutches 7 is interposed between each of motor shafts 30a and each
of axles 30b.
The operation of an over-running clutch used as clutch 7, as shown in FIG.
10 and others, is similar with that of the above described clutch 7 of the
first group, as shown in FIG. 3 and others. With regard to the operation
of the pair of clutches 7 as over-running clutches shown in FIG. 11, they
disengage when motor shafts 30a rotate at the same speed with or slower
than axles 30b, and automatically engage when motor shafts 30b rotate
faster than axles 30b. According to this construction, all of the four
wheels are rotated at the same speed in normal traveling, so that
main-driving wheels 5 drive second hydraulic motor M2 through output shaft
4 and second hydraulic pump P2. In this case, clutches 7 automatically
disengage, so that axles 30b are not driven, thereby causing the vehicle
to travel in two-wheel drive. When either or both of main-driving wheels 5
slip, the traveling speed of the vehicle is reduced, causing the rotary
speed of sub-driving wheels 6 to become slower relative to that of
main-driving wheels 5. Thus, each of clutches 7 automatically engages
between motor shaft 30a and axle 30b, thereby driving sub-driving wheels 6
and causing the vehicle to travel in four-wheel drive.
Next, an explanation will be given on construction for preventing
sub-driving wheels 6 from being dragged in turning according to FIGS. 12
to 18.
For the embodiment shown in FIG. 12, both displacement adjusting means,
like movable swash plates, of the pair of left and right second hydraulic
motors M3 with variable displacement interlock with steering operating
tool 31, so that sub-driving wheels 6 are accelerated in proportion to the
degree of turning operation of steering operating tool 31. This
construction prevents dragging.
For the embodiment shown in FIG. 13, a flow control valve unit 44 is
interposed on oil passages between second hydraulic pump P2 and the pair
of second hydraulic motors M3. Flow control valve unit 44 changes the
quantity of passing oil according to the turning operation of steering
operating tool 31. This prevents the vehicle from dragging and enables it
to turn smoothly.
An embodiment of flow control valve unit 44 will be described according to
FIG. 14. A bypass oil passage 45c is interposed between oil passages 45a
and 45b as a closed fluid circuit. A variable diaphragm 32 is provided on
bypass oil passage 45c so as to interlock with steering operating tool 31.
Variable diaphragm 32 is closed tight in proportion to the increase of
rotational degree of steering operating tool 31, thereby accelerating the
pair of second hydraulic motors M3 for preventing sub-driving wheels 6
from being dragged.
Another embodiment of flow control valve unit 44 is shown in FIG. 15. In
this regard, a pair of flowing adjusting valves, each of which comprises a
variable diaphragm 32 and a relief valve 33, are provided respectively on
oil passages 45a and 45b. A pair of check valves 35 are connected
respectively to a pair of bypass oil passages 45c as primary oil circuits
of the flowing adjusting valves. Each check valve 35 is disposed so as to
allow the primary pressure oil of each flowing adjusting valve to pass
through each variable diaphragm 32. A pair of check valves 34 are provided
so as to allow the secondary oil of the flowing adjusting valves to flow
into the primary oil circuit thereof. Accordingly, the quantity of oil
flowing from high pressure portion to low pressure portion is limited,
thereby accelerating sub-driving wheels 6 during the turning operation of
steering operating tool 31, similar to the above mentioned.
Flow control valve unit 44 may also be constructed as shown in FIG. 16. In
this regard, a pair of variable fixed quotient dividing valves 36 are
interposed respectively on oil passages 45a and 45b. A pair of switching
valves 37 are interposed respectively on a pair of oil passages 45d
between left and right second hydraulic motors M3, so that the secondary
oil circuit of each variable fixed quotient dividing valve 36 is connected
to both primary and secondary oil circuits of each switching valve 37. The
quantity of oil flowing through variable fixed quotient dividing oil
valves 36 can be changed by the turning operation of steering operating
tool 31. Also, when switching valves 37 are switched so as to block oil
passages 45d, pressured oil of the quantity corresponding to the steering
angle is charged from variable fixed quotient dividing oil valves 36 to
left and right second hydraulic motors M2, thereby driving left and right
sub-driving wheels 6.
Next, an explanation of the embodiments shown in FIGS. 17 and 18 will be
given. Here, the displacement of second hydraulic pump P2 is changed
during turning according to the detection of a difference of operating oil
pressure between left and right second hydraulic motors M3. For the
embodiment shown in FIG. 17, second hydraulic pump P2 has variable
displacement and its displacement adjusting means, like a movable swash
plate, is connected with an actuator 40 (a hydraulic cylinder, a solenoid
or so on) which is controlled by a controller 41. If actuator 40 is a
hydraulic cylinder, it is controlled by controller 41 as a servovalve or
so on. A reference numeral CP1 designates a charge pump for driving the
hydraulic cylinder. Controller 41 recognizes the vehicle is turning when
it detects that the pressure of oil charged from second hydraulic pump P2
to left second hydraulic motor M3 is different from that to right second
hydraulic motor M3. At this point, the quantity of oil discharged from
second hydraulic pump P2 is increased, so that sub-driving wheels 6 are
accelerated and prevented from being dragged.
For the embodiment shown in FIG. 18, a switching valve 42 and a pressure
difference detecting valve 43 are replaced with a servovalve in controller
41. Switching valve 42 with two switching stages is interposed between
actuator 40 and charge pump CP2 and is switched by pilot pressure oil
flowing from pressure difference detecting valve 43 through a pilot oil
passage 46. Pressure difference detecting valve 43 is switched by the
difference of the oil pressure between a pair of pilot oil passages 47,
which arc branched respectively from the pair of oil passages 45d
connecting left and right second hydraulic motors M3 with each other. When
there is no oil pressure difference between oil passages 45d in the case
of straight travel, pressure difference detecting valve 43 and switching
valve 42 are not switched. When the difference is generated because of
turning, pressure difference detecting valve 43 is switched, so that pilot
pressure oil flows into pilot oil passage 46. Thus, switching valve 42 is
switched so as to drive actuator 40. Accordingly, the oil discharged from
second hydraulic pump P2 is increased, and left and right second hydraulic
motors M3 are accelerated, thereby preventing sub-driving wheels 6 from
being dragged.
With regard to the embodiment shown in FIGS. 17 or 18, controller 40 and
actuator 41 may also be connected to left and right second hydraulic motor
M3. Alternatively, these embodiments may be employed by the driving
systems of the first group, such that controller 40 and actuator 41 are
connected to second hydraulic pump P2 or second hydraulic motor M2.
Furthermore, for the embodiment shown in FIG. 19, a single sub-driving
wheel 6 is provided. Sub-driving wheel 6 is attached to an output shaft 30
of a single hydraulic motor M3. Thus, only single hydraulic motor M3 is
required to drive single sub-driving wheel 6. The differential gear unit
D2 is omitted, thereby simplifying the driving system so as to be suitable
for a small mower tractor.
The present invention thus far described has the following effects:
First, because the output power of mechanical sub-transmission 3 is
drivingly connected with output shaft 2 of first hydraulic motor M1, which
is fluidly connected with first hydraulic pump P1 and is driven by the
power of engine E through the closed fluid circuit, and drives
main-driving wheels 5 and second hydraulic pump P2 fluidly connected with
second hydraulic motor M2 for driving sub-driving wheels 6, sub-driving
wheels 6 can be optionally changed by second hydraulic pump P1 and second
hydraulic motor M2 according to the stepless transmitting of first
hydraulic pump P1 and motor M1. This allows the vehicle to be switched
between four-wheel drive and two-wheel drive easily and second hydraulic
pump P2 to be rotated at a speed corresponding to the adjustment of the
traveling speed.
In this construction, since main-driving wheels 5 are driven by first
hydraulic motor M1 and sub-driving wheels 6 are driven thereby through
clutch 7 acting as an over-running clutch, driving power is automatically
transmitted into sub-driving wheels 6. This occurs in case of slipping of
either of the main-driving wheels 5, so that the vehicle can easily escape
from being stuck, thereby preventing the ground surface from being
injured. In cases where clutch 7 is a manual clutch, manual operation of
collecting clutch 7 enables the vehicle to easily escape from being stuck.
Also, since clutch 7 acting as an over-running clutch is interposed between
output shaft 4 of sub-transmission 3 and input shaft 9 of second hydraulic
pump P2, changing of the rotary speeds of main-driving wheels 5 and
sub-driving wheels 6 can be easily detected, so that driving power can be
rapidly given to sub-driving wheels 6.
Since second hydraulic pump P2 or motor M2 has variable displacement, the
rotary speed of sub-driving wheels 6 can be easily changed.
Also, since second hydraulic pump P2 or motor M2 with variable displacement
is connected with steering operating tool 31 so as to increase the rotary
speed of sub-driving wheels 6 in proportion to the degree of turning
operation of steering operating tool 31, sub-driving wheels 6 can be
accelerated corresponding to the turning radius, thereby enabling the
vehicle to turn easily.
Since output shaft 2 of first hydraulic pump P1 and output shaft 14 of
sub-transmission 3 are longitudinally disposed and drivingly connected to
first differential gear unit D1 for main-driving wheels 5 through bevel
gears 16 and 17, transmission casing 1 can be laterally narrow, so as to
be compacted.
Alternatively, since output shaft 2 of first hydraulic pump P1 and output
shaft 14 of sub-transmission 3 are laterally disposed, they can be
drivingly connected to first differential gear unit D1 for main-driving
wheels 5 through plain gears 16' and 17', thereby improving the efficiency
of transmitting into second differential gear unit D2. Additionally, this
construction allows transmission casing 1 can be longitudinally short, so
as to be compacted.
Secondly, because the output power of mechanical sub-transmission 3 is
drivingly connected with an output shaft 2 of first hydraulic motor M1,
which is fluidly connected with first hydraulic pump P1 and is driven by
the power of engine E through the closed fluid circuit, and drives
main-driving wheels 5 through first differential gear unit D1 and drives
second hydraulic pump P2 fluidly connected with second hydraulic motor M2
for driving sub-driving wheels 6 through second differential gear unit D2,
axles 18L and 18R with main-driving wheels 5 and axles 25L and 25R with
sub-driving wheels 6 are fluidly connected. Thus, a transmitting shaft is
not required to be disposed at the venter portion of the vehicle. This
allows the space between axles 18L and 18R and axles 25L and 25R to be
expanded, so as to provide a large space for attachment of a mid-mount
working machine like side reel mowers 8SL and 8SR.
Thirdly, because the output power of mechanical sub-transmission 3 is
drivingly connected with an output shaft 2 of first hydraulic motor M1,
which is fluidly connected with first hydraulic pump P1 and is driven by
the power of engine E through the closed fluid circuit, and drives
main-driving wheels 5 through first differential gear unit D1 and also
drives second hydraulic pump P2 fluidly connected with a pair of left and
right second hydraulic motors M3 for driving left and right sub-driving
wheels 6 respectively, axle casing 23 containing axles 25L and 25R with
sub-driving wheels 6 therein can be made more compact and light.
In this construction, since second hydraulic pump P2 or left and right
hydraulic motors M3, which have variable displacement, is connected with
steering operating tool 31 so as to increase the rotary speed of
sub-driving wheels 6 in proportion to the degree of the turning operation
of steering operating tool 31, the rotary speed of sub-driving wheels 6
can correspond to the degree of the turning radius when turning. This
allows the vehicle to turn smoothly without dragging of sub-driving wheels
6.
Also, since flow control valve unit 44, interposed on the oil circuit
between second hydraulic pump P2 and second hydraulic motors M3, is
connected with steering operating tool, the similar effect can be
obtained.
Furthermore, since the pair of decelerator casings 29, disposed on both
lateral sides of left and right front axle casings 52 respectively,
project horizontally forward, space P can be provided between left and
right decelerator casings 29, so that a working machine like middle front
reel mower 8FM provided in space P can be disposed compactly. The working
machine is also, then, protected by decelerator casings 29 and driving
wheels 5 and 6. Also, the working machine can be disposed between
main-driving wheels 5 and sub-driving wheels 6, so as to be limited in its
forward projection. This shortens shortening the length of the working
vehicle provided with the working machine. Also, an arm for suspending the
working machine like middle front reel mower 8FM can be shortened, and in
the case where a plurality of working machines like triple reel mowers
8FL, 8FM and 8FR are provided, the range of their overlap can be
shortened.
A lifting mechanism for working machines like triple front reel mowers 8FL,
8FM and 8FR can also be disposed in space P, so that space P can be
advantageously utilized. Also, the lifting mechanism can be disposed at
the longitudinal and lateral middle of the vehicle body, thereby giving
the vehicle a good balance of weight and enabling it to travel steadily.
Furthermore, since each decelerator casing 29 is disposed horizontally
rather than vertically, the vehicle body can have a low center of gravity
so as to travel steadily.
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